Is transform another name is a gameObject? When the docs are talking about parenting here, they mention the parent of the transform. What does this mean?
a Transform is not a gameObject but when you are talking about parents and children that is in the transform class
It's referring to the transform of the parent of the current gameObject's transform.
If that confuses you look at some examples. This sets the parent of the gameObject the script it is attached to:
transform.parent = anotherGameObject.transform;
Or a gameObject could set itself to be the parent of another gameObject(this script would be attached to the parent):
anotherGameObject.transform.parent = transform;
Hopefully that helps you understand better. It's very intuitive once you wrap your head around it.